Device for removing sharp edges from spaced projections



y 7, 956 J. o. CREEK 2,754,636

I DEVICE FOR REMOVING SHARP EDGES FROM SPACED PROJECTIONS Filed Feb. 24, 1955 mveNToL J. o. C@K 5v ATTO wa s DEVICE FOR REMOVING SHARP EDGES FROM SPACED PROJECTIONS John Oliver Creek, Brampton, Ontario, Canada, assignor to Orenda Engines Limited, Malton, Ontario, Canada, a corporation Application February 24, 1955, Serial No. 490,320

4 Claims. (Cl. 51-141) This invention relates to a device for removing burrs from a work-piece, resulting from a previous machining operation.

The invention will be described as relating in particular to a device for removing burrs from the machined edges of a gas turbine part but it will be appreciated that this application is illustrative of its function which is not to be construed as limited thereto.

It is common in certain types of gas turbine engines to accurately position the nozzle guide vanes, sometimes also termed the turbine stator blades in radially milled slots in an annulus at both their inner and outer ends. These slots are accurately machined in two annuli providing two surfaces for the root and tip of the blade to bear against. Each slot that is machined acquires eight sharp edges that must be deburred or rounded and since each blade requires two slots and since there are from eighty to one hundred blades it will be appreciated that deburring of these edges by hand tools or by hand manipulated power tools is a relatively lengthy operation. Such methods also have the further disadvantage that the consistency of the work is dependent upon the operators skill.

The invention proposes to revolve the annulus in which the slots have been milled while maintaining abrasive units in spring biased engagement with the edges of the slots in such a manner that the abrasive carrying surface is automatically passed over the edges of the slots and removes any burrs which may be present.

The preferred embodiment of the invention will now be described with reference to the accompanying drawings in which like reference numerals refer to like parts in the various views and in which:

Fig. 1 is a perspective view of the device in operation upon a work-piece, and

Fig. 2 is a detailed front elevation of one abrasive unit.

Referring now to the drawings it will be seen that the machine consists of a frame having a base plate 10, substantially vertical supporting members 11 and a top plate 12. A rotatable table 13 is mounted on shaft 14 which is journalled in bearings 15 and 16 mounted in the upper and lower plates respectively. A disc 17 is keyed to shaft 14 for rotation therewith, the keyway extending a substantial distance along the shaft 14 so that disc 17 may slide along shaft 14 while remaining in rigid angular engagement with it. A yoke 18 having two arms 19 and 20 is mounted on a vertical member 21 which is journalled in bearings 22 and 23 in the upper and lower plates respectively. The arm 20 of yoke 18 extends beneath the disc 17 while the arm 19 extends above itv Both arms 19 and 20 terminate in annular collars 24 which encompass shaft 14 which lie adjacent disc 17 above and below it. The vertical member 21 is provided with screw threads along its length which engage with internal screw threads in hole 25 in yoke 18 through which member 21 passes. A portion 26 of member 21 has been formed to a square cross-section to provide bearing surfaces for a wrench or similar tool. By turning member 21, the yoke 18, by viratent O 2,754,636 Patented July 17, 1956 tue of the threads, is caused to rise or fall. The peripheral edge of disc 17 is provided with a frictional rim at 27 which is in engagement with the face of a driven wheel 28. Wheel 28 is mounted on shaft 29 of a motor 30. The face 31 of wheel 28 is provided with a friction surface to engage the friction rim 27 of disc 17. The rotation of wheel 28 by motor 30 in a counter-clockwise direction will cause the clockwise rotation of disc 17 and hence table 13. By raising or lowering the position of disc 17 with respect to the axis of the Wheel 28 the speed of table 13 can be controlled. The closer the edge 27 of disc 17 is to the axis of wheel 28 the slower the table 13 will revolve. The speed of rotation of table 13 will increase as the edge of disc 17 approaches the edge of wheel 28. If it is desired to reverse the direction of rotation of table 13 then disc 17 must be elevated to a position above the centre of wheel 28 where its speed in the reverse direction may be controlled in a manner similar to that previously described.

Mounted on the table 13 and concentric therewith is a work-piece 32. As was explained earlier the invention will be described with reference to a gas turbine engine part although the device is not limited in its application thereto. The work-piece 32 is an annular member having slots 33 cut in one edge leaving teeth 34 extending upwardly therebetween. It is from the edges of these teeth 34 that the burrs are to be removed. It will be seen that each tooth 34 has four top edges, two outside edges and two inside edges each of which must be treated by an abrasive. For this purpose abrasive units indicated generally at 36 are slidably mounted on support members 35 which extend upwardly from the upper plate 12 beyond the upper surface of work-piece 32. Collars 37 on abrasive units 36 engage support members 35 and can be secured in position by means such as conventional set screws.

From Fig. 1 it will be seen that of the three abrasive units, 36A, the upper unit, bears against the top edges of teeth 34, 36B, the outer unit, bears against the outside edges and 36C, the inner unit, bears against the inside edges of the teeth; the three units are similar in principle but have slight differences in detail which will be brought out below.

Secured to collars 37 by means of arms 38 are mounting plates 39 which carry the components of the abrasive units. A detailed description will be given of the unit 36A which bears against the upper edges of the teeth 34 with reference to Fig. 2.

In Fig. 2 it will be seen that the mounting plate 39 is triangular in form and carries three shafts 40, 41 and 42, one shaft being mounted at each vertex. Shaft 41 is mounted on a block 43 which is slidably engaged in" a slot 44 which lies parallel to the base 45 of the triangular plate 39. A spring 46 lies in the slot 44 and urges the block 43 and the shaft 41 in a direction away from the shaft 40. The two shafts 40 and 41 each have rotatably mounted thereon a pulley 47 and 48 respectively while shaft 42 carries a sprocket or gear wheel 49. Substantially midway between sprocket or gear wheel 49 and pulleys 47 and 48 are two further idler pulleys 50 and 51 mounted on shafts 52 and 53 respectively. An abrasive belt 54 is carried by the four pulleys and the sprocket and passes outside the pulleys 47 and 48 and sprocket 49 and inside pulleys 50 and 51. The spring urged pulley 48 exerts a constant tension on the belt 54 and maintains it in a reasonably taut condition.

Referring again to Fig. 1 it will be seen that the unit 36A which has just been described has been adjusted in its position on supporting member 35 so that the teeth 55 of the sprocket 49 extend downwardly and into the slots 33 between teeth 34. The position is adjusted so that the teeth 55 do not extend completely to the bottom of slots 33 but enter the slots a distance sufiicient to ensure that the abrasive belt 54 will bear against the upper edges of the teeth 34. This may be clearly seen in Fig. 2.

A similar description would serve to describe the construction and positioning of the other two abrasive units 36B and C. The unit 360 which contacts the inner side edges of teeth 34 differs only from the unit contacting the top surfaces in their relative positions. The unit 363 which contacts the outer side surfaces, however, is carried by a mounting plate 39 which is also triangular in shape but in which the distance from the sprocket carrying vertex of the triangle to the base is considerably less than is the case in the other two units as it is necessary for this unit to occupy the smaller space between the outside of the Work-piece 32 and the support member 35. In all other respects the units are similar.

It will be noted that none of the belts 54 are provided with driving means. The only motivating power in the device is the motor 31 which, through the friction drive, drives table 13 and with it Work-piece 32. As workpiece 32 revolves in either a clockwise or counter-clock- Wise direction the action of teeth 34 of the work-piece against teeth 55 of the abrasive belt-carrying sprockets causes rotation of these sprockets and hence imparts motion to belt 54. This motion causes belt 54 to move over the edges of the teeth 34 and, by virtue of its abrasive qualities, removes any burrs that may be present thereon. As is the case with all gears in mesh, there is relative sliding motion between the adjacent side faces of the gear teeth. This, of course, causes relative motion between the projections 34 and the belt 54.

The sprockets or gear wheels 49 may preferably be made of a rubber or rubber-like material. The belt 54 may be of the commercial canvas back type which is provided with any suitable abrasive surface such as emery stone or Carborundum in powdered form adhered to its surface. An alternative method is to provide the surfaces of teeth 55 on gear wheels 49 with an abrasive and in this case the belt 54 may be dispensed with. A further alternative is to use a rubber or rubber-like sprocket 49 without the abrasive belt 54 and apply an abrasive paste thereto when the device is in operation, or an abrasive impregnated rubber or plastic sprocket 49 may be used.

In operation the height of disc 17 is adjusted to provide the optimum operating speed which can quickly be determined by experiment. After the machine has run for a sufiicient length of time in one direction the rotation of table 13 and work-piece 32 is reversed and thus insures that each surface will be subject to a uniform abrading action.

From the foregoing description it will be seen that a device has been provided which will quickly and accurately remove burrs from machined edges.

What I claim as my invention is:

1. A device for deburring an annular workpiece having radially milled slots in an edge producing spaced, axially extending teeth comprising a frame, a rotatable work-carrying table journalled in the frame, at least one abrasive unit adapted to engage the workpiece, the abrasive unit comprising a mounting plate on which are carried rotatable pulleys lying one at each vertex of a triangle, the pulley adjacent the workpiece having the external contour of a spur gear, a belt having an external abrasive surface passing around the pulleys and adapted 4 to be forced into engagement with the workpiece by movement of the abrasive unit towards the workpiece to cause the gear-shaped pulley to be rotated by the engagement thereof with the workpiece.

2. A device for deburring an annular workpiece having radially milled slots in an edge producing spaced, axially extending teeth, comprising a frame, a rotatable work-carrying table journalled in the frame, at least one abrasive unit adapted to engage the workpiece, the abrasive unit comprising a mounting plate on which are carried rotatable pulleys lying one at each vertex of a triangle, the pulley adjacent the workpiece having the external contour of a spur gear, a belt having an external abrasive surface passing around the pulleys and maintained in tension by means of a spring biased idler pulley, the belt being adapted to be forced into engagement with the workpiece by moving the abrasive unit towards the workpiece until the gear-shaped pulley engages the axially extending teeth on the workpiece through the abrasive belt, rotation of the workpiece causing rotation of the gear-shaped pulley and, thus, relative movement between the workpiece and the abrasive belt.

3. A device for deburring an annular workpiece having radially milled slots in an edge producing spaced, axially extending teeth, comprising a frame, a rotatable work-carrying table journalled in the frame, at least one movable abrasive unit adapted to engage the workpiece, the abrasive unit comprising a mounting plate on which are carried three rotatable pulleys lying one at each vertex of a triangle, one of the two pulleys remote from the workpiece being spring biased away from the other pulley, the pulley adjacent the workpiece having the external'contour of a spur gear, a belt having an external abrasive surface passing around the pulleys and adapted to be forced into engagement with the workpiece by moving the abrasive unit towards the workpiece to cause the gearshaped pulley to engage the workpiece through the abrasive belt and to be rotated by rotation of the workpiece.

4. A device for deburring an annular workpiece having radially milled slots in an edge producing spaced, axially extending teeth, comprising a frame, a rotatable work-carrying table journalled in the frame, a plurality of movable abrasive units adapted to engage the workpiece, one abrasive unit being adapted to engage the free edge thereof, a second movable abrasive unit being adapted to engage the inner surface of the workpiece and a third movable abrasive unit being adapted to engage the external surface of the workpiece, each abrasive unit comprising a mounting plate on which are carried three rotatable pulleys lying one at each vertex of a triangle, one of the two pulleys remote from the workpiece being spring biased in a direction away from the other of said pulleys, the pulley adjacent the workpiece having the external contour of a spur gear, a belt having an external abrasive surface passing around the pulleys and adapted to be forced into engagement with the workpiece by movement of the abrasive unit towards the workpiece to cause the gearshaped pulley to engage the spaced projections on the workpiece through the abrasive belt so as to be rotated by rotation of the workpiece.

References Cited in the file of this patent UNITED STATES PATENTS 

